It is well known that energy radiated in the form of light is capable of inducing and/or promoting certain photochemical reactions and that different photochemical reactions are induced by the action of light rays (or photons) of various wavelengths. Certain wavelengths of light, especially those in the blue and ultraviolet range, are known to be injurious to the eye.
Dyed lenses, when used with prescription or non-prescription sunglasses are basically intended to fulfill one of two functions: the first function is either selective or overall reduction of the injurious light and radiation. Lenses dyed for this purpose are known as protective lenses. Protective lenses may block harmful wavelengths either by reflection or, more commonly, by absorption. The second function is fulfilled by lenses which fulfill cosmetic requirements and are referred to as fashion tints. Combination dyes covering both requirements are also available.
In the current art, there are protective lenses that block blue and ultraviolet wavelengths and there are separate polarizing lenses that block horizontally polarized incident light. The combination of a polarizing and a blue and ultraviolet blocking lens is not currently available as confirmed by a listing of lenses published in 1986 by Retinitis Pigmentosa International and a search of the advertising literature. The non-availability of these combination lenses is due, in part, to the little research that has been conducted by sunglass companies on the detrimental effect of the blue light hazard to the retina of the eye and the technical problems encountered in combining the temperature-sensitive polarizing film with the dye. This problem has been solved by the instant invention by selecting dyes that can provide the required blue blocking at a temperature that will maintain the usefulness and structural integrity of the polarizing film.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. However, the following U.S. and foreign patents were considered related:
______________________________________ PATENT NO. INVENTOR ISSUED ______________________________________ 4,261,656 Shy-Hsien Wu 14 April 1981 2,307,602 (DE) Krumeich 29 August 1973 3,588,216 Bloom 28 June 1971 3,460,960 Francel et al 12 August 1969 2,643,982 Riley 30 June 1953 ______________________________________
The Shy-Hsien Wu patent discloses a transparent, optically clear article that consists of a glass or plastic base element that supports a thin and delicate organic or inorganic surface film such as a plastic polarizing film. The film is protected from the damaging effects of moisture, scratching and abrasion by a protective plastic coating. The hardness of the protective coating is controlled to avoid excessive flexibility or brittleness, so that good scratch resistance over a relatively soft film is obtained.
The Krumeich German Offenlegungsschrift discloses an optical filter that corrects red/green color blindness. The filter is designed so that in the blue to green range of the visible spectrum, the spectra curve progresses at a constant rate at very low values and increases steeply to a high value in the green to red range. The filter is particularly advantageous if its spectra curve has a permeability of under 0.01 percent in the blue to green range and a transmission that increases to approximately 100 percent in the red range. The Bloom patent discloses an element for filtering infrared light. A metal complex is employed as an infrared absorber in which the metal is a metal of the first, second or third transition metal series which will provide a complex that is an effective infrared absorber and which is effectively transparent to light in the visible region of the spectrum.
The Francel et al. patent discloses a method of coating a vitreous substrate, such as glass, with a fluid coating composition. The coating imparts to an otherwise clear and/or transparent glass substrate the light transmittance characteristic of amber or darker glass. The simulated amber glass obviates the necessity of having separate amber glass, batch-melting and auxiliary manufacturing apparatus and related equipment.
The Riley patent discloses an absorbent liquid coating composition that forms a film that is applied as a protective and/or decorative coating to glass and other normally transparent or translucent materials. The film has the properties of absorbing substantially all the wavelengths of ultraviolet, violet and blue light below approximately 490 nanometers and substantial amounts of wavelengths from 630-750 nanometers. The film allows the transmission of selected wavelengths above 490 nanometers.